201328520133048399FFD1362B-FFBB-FFA1-FF94-9D79FFDA284457760639C569AF-2376-4FA2-9204-A6F0B81A597011220121532013Helena V. Shaverdo, Lars Hendrich, Michael BalkeThis is an open access article distributed under the terms of the Creative Commons Attribution License 3.0 (CC-BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.urn:lsid:zoobank.org:pub:39C569AF-2376-4FA2-9204-A6F0B81A5970Abstract

Exocelina baliemsp. n. is described from the Baliem Valley in the Central Mountain Range of New Guinea (Papua Province, Indonesia). Having striolate elytra, different structure and setation of the male and female genitalia and tarsomeres, and inhabiting swampy ponds, the new species differs from all known New Guinea species, which have smooth elytra and are stream associated. It forms a monophyletic group with the Australian Exocelina ferruginea (Sharp, 1882) and New Caledonian Exocelina inexspectata Wewalka, Balke & Hendrich, 2010, based on shape of the paramere and structure of the male tarsi. Habitus, protarsomeres, and male and female genitalia are illustrated, comparing some structures with Exocelina ferruginea and two New Guinea stream species. We briefly discuss the biogeographic relevance of this discovery.

The Australasian Copelatinae genus Exocelina Broun, 1886 (= Papuadytes Balke, 1998, see Nilsson and Fery 2006 and Nilsson 2007) is a current taxonomic and molecular phylogenetic research focus (Balke and Bergsten 2003; Balke et al. 2004a, 2004b, 2007; Watts & Humphreys 2009; Wewalka et al. 2010). Here, we continue our study of the highly diverse New Guinea Exocelina fauna, with 63 formally described species (Balke 1998, 1999, 2001; Shaverdo et al. 2005, 2012). These species form a morphologically homogenous, monophyletic group associated with streams and rivers (e.g. Balke et al. 2007). In the present paper, we describe a new species, which is morphologically distinct and ecologically different from all other known New Guinea species. The closest related species to the new one occur in Australia and New Caledonia.

All specimen data are quoted as they appear on the labels attached to the specimens. Label text is cited using quotation marks. Our red identification labels were attached to the types.

Measurements were taken using a Leica M205C stereomicroscope. The following abbreviations were used: TL (total body length), TL-H (total body length without head), and MW (maximum body width). Drawings were made with the aid of a camera lucida attached to a Leica DM 2500 microscope. For detailed study and illustration, protarsi and genitalia were removed and mounted on glass slides with DMHF (dimethyl hydantoin formaldehyde) as temporary preparations. The drawings were scanned and edited, using the software Adobe Illustrator CS5.1.

The terminology to denote the orientation of the genitalia (“ventral” for median lobe and gonocoxae and “dorsal” and “external” for paramere) follows Miller & Nilsson (2003). Administrative divisions of Indonesia follow information from Wikipedia (2013).

Beetle middle-sized, piceous, with reddish brown head; both sexes matt, dorsal surface with strong dorsal microreticulation and numerous, short strioles; male antennomeres simple; male pro- and mesotarsomeres 1–3 distinctly dilated, male protarsomere 4 modified, with large, thick anterolateral hook-like seta, male protarsomere 5 simple, with relatively long setae and long claws, anterior claw with fine serration ventrally; median lobe with continuous outline in ventral view, ventral sclerite with a strip of sclerotization on right side, proximal part of median lobe striolate; paramere without notch on dorsal side but with a long prolongation of subdistal part; female metatarsi without ventral row of natatorial setae; gonocoxae with prolonged, slightly pointed apices. This is the only New Guinea species of Exocelina with a striolate dorsal surface.

Surface sculpture: Head with dense, coarse punctures (spaces between punctures 1–3 times size of punctures, diameter of punctures much larger than diameter of cells of microreticulation) on middle, anterior part of head with finer punctation, between and behind eyes with very short but distinct longitudinal strioles, vertex with fine, sparse punctation. Pronotum with numerous short longitudinal strioles, distinctly shorter and sparser on disc, disc also with coarse punctures. Elytra densely covered with numerous short longitudinal strioles, posterior third of elytra with transverse shackle-like strioles, and elytral lateral margins with transverse strioles and coarse punctures. Head, pronotum, and elytra with strongly impressed microreticulation, dorsal surface matt. Metaventrite and metacoxa distinctly microreticulate. Metacoxal plates densely covered with short longitudinal strioles and in anterior part also with transverse wrinkles. Abdominal ventrites with finer microreticulation and fine sparse punctation, more evident at their middle. Ventrites 1–2 with numerous longitudinal striae, ventrites 3–5 with finer, shorter, transverse strioles, and ventrite 6 with long sublongitudinal strioles.

The species was collected from a small pool in a riverine relic forest close to the Baliem River, approximately 1 km from the runway of Wamena airport (Fig. 9). The beetles were found between roots, leaves, and emergent water plants in the shallow water, at the shady edge of the pond underneath a large tree. One specimen was collected from a tuft of Phragmites after the pool had dried up during the rather dry summer in the following year (1993). The new species was associated with the following dytiscids: Hydrovatus enigmaticus Biström, 1997, Hyphydrus dani Biström, Balke & Hendrich, 1993, Hydaticus okalehubyi Balke & Hendrich, 1992, and Rhantus dani Balke, 2001. We revisited the area in winter 2011 and found that most ponds were highly eutrophic (as foreseen by Balke 1993), large trees had mostly disappeared, and the species was not found again during a quick survey. We assume that the type locality has been destroyed, but other suitable habitats might exist elsewhere in the vast valley.

The species is named after the type locality, the Baliem River Valley. The name is a noun in the nominative singular standing in apposition.

Comparison and discussion

The new species is morphologically similar to the Australian Exocelina ferruginea (Sharp, 1882) and the New Caledonian Exocelina inexspectata Wewalka, Balke & Hendrich, 2010. It shares with them some characters not found in all other known New Guinea Exocelina and listed below.

1) Striolate elytra (Fig. 1); in Exocelina ferruginea and Exocelina inexspectata elytra without strioles on anterior (basal) 2/3 but with distinct punctures, and in posterior (apical) third with transverse strioles. The striolate dorsal surface of the body is also characteristic for other Australian and New Caledonian species. All other New Guinea species have punctation rather than strioles on elytra.

2) Modification of paramere: prolongation of subdistal part on dorsal side (Figs 4A, 4B). This apomorphic character is observed only in these three species.

3) Presence of a strip of sclerotization on right side of ventral sclerite of median lobe (Figs 5A, 5B). This character is also present in Exocelina ferruginea. The holotype of Exocelina inexspectata is teneral so this character is not evident, but is characteristic for several other New Caledonian species, e.g. Exocelina novaecaledoniae (J. Balfour-Browne, 1939), Exocelina ouin Wewalka, Balke & Hendrich, 2010, and Exocelina jeannae Wewalka, Balke & Hendrich, 2010.

4) Striolate surface of proximal part of median lobe (Fig. 6). It is characteristic of Australian species.

The above mentioned modifications of pro- and mesotarsus are characteristic of all known Australian species, with some small variations.

- Anterior claw with fine serration ventrally. This character is also observed in Exocelina ferruginea and Exocelina inexspectata.

- Posterior protarsal claw evenly curved, with two fine denticles on ventral margin. This character is also present in Exocelina ferruginea.

6) Female metatarsi without ventral row of natatorial setae. It is characteristic of known Australian species (in Exocelina australiae (Clark, 1863) also for males).

7) Shape and setation of gonocoxae: apices not rounded, slightly pointed, setation much sparser (Fig. 7A). The gonocoxae of Exocelina baliem are evidently different from those of other New Guinea Exocelina species (Fig. 7C and Fig. 17b in Shaverdo et al. 2005) and much more similar to the gonocoxae of Exocelina ferruginea (Fig. 7B).

Exocelina baliem sp. n. is unique among known New Guinea Exocelina species in its habitat requirements. It inhabits ponds, unlike all other known species of Exocelina in New Guinea, which occur in directly stream related stagnant water, such as rockpools, stagnant backflows, marginal puddles and waterholes along stream banks, and at the immediate stream margin. The habitat of Exocelina baliem sp. n. is similar to that of the closely related Exocelina ferruginea.

Balke et al. (2007) showed that New Guinea Exocelina species form a monophyle-tic group, the result of a single colonization from Australia, and that Australian species, including Exocelina ferruginea, form a "basal" paraphyletic series, followed by the other Exocelina species. Thus, being closely related to Exocelina ferruginea, Exocelina baliem sp. n. represents an older colonization from Australia into New Guinea, but without subsequent radiation. This radiation likely occurred more recently, producing the highly diverse clade of morphologically distinct stream species. Also we assume that New Caledonia was colonized three times out of Australia, not twice as suggested by Balke et al. (2007), since the New Caledonian Exocelina inexspectata is closely related to Exocelina baliem sp. n. and Exocelina ferruginea. The species is known only from the holotype collected at light, and it might also be a pond species, whereas all other known New Caledonian species are stream associated.

Acknowledgements

We are grateful to Dr. H. Schillhammer (Vienna) for his photographic help and to Dr. T. Galloway (Winnipeg) for his linguistic review of the manuscript.

Financial support of the study was provided by the FWF (Fonds zur Förderung der wissenschaftlichen Forschung – the Austrian Science Fund) through a project P 24312-B17 to the senior author. Michael Balke was supported by the UK Darwin Initiative and the German Science Foundation (various projects since BA2152/2-1).

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